Currently I’ve just been using normal Diffuse maps for everything. And I finally have gotten my head around metal/roughness/specualar. But I haven’t really been able to understand the purpose of albedo maps. And I haven’t found good instructional videos or written tutorials about this.
Well the big thing in materials these days is whats called PBR or in long hand Physics Based Rendering.
The nature of physics based rendering is the need for the material to interact and behave across the entire surface as would occur to it’s real world counter part so for the color/diffused map to work like the real deal it needs to excluded lighting information that is usually included by the use of a photo sourced texture.
This is where the Albedo texture map comes it as although it is similar to a photo sourced texture it excludes all surface reactions to spec and gloss usually introduced by a directional light source.
The benefit is a procedural material type low in resolution but can be mapped at the detail level using the color mask usually supplied with the material.
Here is an excellent tutorial that puts it all together and you can follow along with the supplied textures.
http://gametextures.com/blog/2014/09/30/using-gametextures-in-unreal-engine-4/
So I tried out this example directly in UE4: PBR Tutorial Series - Community & Industry Discussion - Epic Developer Community Forums
But the glossiness made it way more shiny than what he did, so I had to brighten the glossiness map up quite a bit. Is the PBR a bit different in UE4 than in marmoset? or is there some settings I have overlooked?
Other than having to make the glossiness brighter, there result was quite satisfying.
There will always be a difference between how one application handles materials versus another and for sure making a top notch material “is” a difficult task that is up there with achieving perfect lighting. Everything else being what it is with out the two what you land up with is mush.
To get a material to look right though, and a common mistake, one needs to set up their material on objects that moves as a static single frame render does not tell the whole story of whats going on and spinning it around in a standalone scene only applies half the lighting information needed to make the material look “physically” correct. You need the key light but you also need the renderosity effect created by light bouncing off of surfaces around it.
My process is simple by using one of the already available sample sets and animate a simple sphere object moving around into different areas of lighting and lighting levels which reacts differently as to changes in the source lighting rather than changes from the viewer perspective.
If you think about it it makes more sense to move the material though different lighting conditions than how it would look under one. 
P.S. Just an after though but a real world rough surface can look glossy at a given angle or even reflective.
Thanks man. I’m definitely heading the right direction, getting pretty decent materials set up and its the same with lighting. The example scenes are a big help to see how they generally do all of this. Being used to the normal workflow is throwing me off some, but I can see how it is much easier if materials behaved correctly under all types of lighting conditions. And also it can save time.
Here is my latest scene; most of the materials don’t use albedo maps.
Well there is absolutely nothing wrong with that.
Good lighting, good material use so no problems there.
To be picky to point out whats not right.
It’s computer perfect.
Add some scratches and damage to get the computer out of the render and you home free.
(Photoshop is you friend)
What you’ve got looks good, so just practice thinking about how Albedo maps work as you slowly get used to PBR. The thing is, many “diffuse” maps work perfectly well as albedo, like that wood in your scene. If it’s evenly lit and doesn’t have shading or highlights, then a good photo can be an albedo map without trying to make it complicated. On the other hand, certain common real-life materials have very specific values for Albedo and a photograph can’t be trusted. Check out some of the examples on this documentation page, under Base Color. Physically Based Materials in Unreal Engine | Unreal Engine 5.1 Documentation. You think fresh snow is bright white? Nope, grey.
You said that your roughness map turned out super glossy inside Unreal but not Marmoset. This was, in fact, (most likely) an oversight on your part. The same thing happened to me when exporting a roughness map from Substance Painter. When importing a map that has a very specific value for something like roughness or an alpha map, you should uncheck the sRGB box inside the texture. The same way that normal maps uncheck it by default because the RGB values need to be precise and not gamma corrected like most textures.
Also, the Tutorial talks about Gloss and not Roughness So if you invert the Gloss map you should get a perfect Roughness map that is not super glossy^^ (and yep, deactivate sRGB) 
Even if you work with PS set to sRGB color and gamma 2.2? But wow, that makes sense that you need to invert them. I really thought glossiness and roughness where the same thing.